Telephone-exchange system



March 19, 1929. v G, THQMPSQN 1,705,947

TELEPHONE EXCHANGE SYSTEM Filed May 17, 1927 4 Sheets-Sheet l Mms/NAL luf-N^ March 19, 1929. G. THoMPsoN TELEPHONE EXCHANGE SYSTEM 4 sheets-sheet 2 Filed May 17. 1927 www new w Mardi 19, 1929. G, THOMPSQN 1,705,947

4 .TELEPHONE EXCHANGE SYSTEM Filed Maya?. 192'? 4 sheets-sheet 3 Joa le l ifn Mmm.

i; u; l v I' /NvfNro/i: 1 :fifa/mf THUMPJON Arr Er 4 Sheets-Sheet 4 March'19, 1929. G. THOMPSON TELEPHONE EXCHANGE SYSTEM Filed'May 17, 1927 w. .QQ

/m/E/v TUR: @50H65 foMPso/v rlChe sender thereuponcontrols the switches Patented Mar. 19, 1929.

UNITED STATES PATENT OFFICE.

GEORGE THOMPSON, OF MOUNT VERNON, NEW YORK, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED,` OFNEW'YORK, N'.' Y., A CORPORATION 0F NEW YORK.

Application` led May 17,

lThis invention relates to telephone exchange systems and its object is to improve systems for the establishment and control of toll switching connections. n

According to the invention, current. for ringing the called subseribers line is supplied from the final switch, but in case the. called subscriber is recalled ringing current for this purpose is applied at a preceding group selector' under control of the operator, the selection of the proper kind of current at the group selector for partly line eallsbeing under control of the final switch and independent of the operator. y y y y The invention is illustrated in a toll system employing automatic selective switches of the revertive control type the movement of which is controlled by a common register sender. The toll operator by means of a dialing cord circuit extends the toll connection to an automatic switch andrrecords the calledl line designation on an idle register sender.

to extend the connection to the called line. Since the subscribers lines seized by the final switch may include party lines, different kinds of ringing current must be supplied. The party lines are provided with a set of terminals per station and all lines requiringa given kind of ringing current are segregated to appear before the same group of final switches. These finals are arranged to apply ringing current inthe proper manner for sigyand 4 are .of the power drive rotary type the construction of which is illustrated in the vpatent to McBerty, No. 1,097,868, granted naling the part-y line subs'tations to which they have access. i

(in the connection first being extended to a called party line the called substation is signaled by ringing current supplied from the final switch the same as for a local connection, but under control of the toll operator. Aln case the toll operator wishes to recall the called subscriber it is necessary that she be provided with means for causing the appliration ci the proper kind of ringing current to the called line. It is'also desirable that this be done without releasing and reestablisliing the connection. Accordingly the present invention contemplatesyV an arrangement in which the nal switch, which identilies the kind of ringing current needed, causes a record to be set up in a preceding group selector in the series. This record in the group selector becomes effective under the control TELEPHONE-EXCHANGE SYSTEM.

1927. serial No.. 192,116.V

of the tolloperator when the recall is made to cause the application of' ringing current .from

Vthel group selector. In vthis manner the final n switch is not disturbed in any way, it 1s not Y and also illustrates a toll connection'extended to her position.` y

Fig. 2 shows an incoming or first group selector to which toll connections are extended. It also illustrates diagrammatically a common register sender.

Fig. 3 shows a diagram of a second group selector. n

Fig. 4 shows afinal selector switch having access to called lines. i

The toll operators cord of any suitable design, the particular circuit shown being .similar to that shown and decircuit 130 may be scribed in detail in the patent to Stokely, No.

1,474,008, granted November 13, y1923 vand in the `application of Stokely, `Serial No. 21,756, iiled April 9, 1925 Patent- No. 1,653,789, granted Dec. 27, 1927.

The selector switches shown in Figs.l 2, 3

,system the detailed operation will now be explained. For this purpose assume that the subscriber of line 100 wishes to extend a toll connection to a subscriber on the party line 127. The calling-subscriber initiates the callV inthe usual manner which is answered by/an operator at position 120. After the necessary '102 oi the cord circuit 130 into jack 101. The toll operator, after receiving the number ot the called line, seizes the plug 103 and tests the jack 203 of the trunk leading to the incoming switch shown in Fig. 2. llt the trunk is idle she inserts the plug 103 in ack 203 coinpleting a circuit as itollows: trom the grounded sleeve ot the jack 203, sleeve ot the plug 103, right winding ot relay 107, windings ot relays 106 and 105 to battery. rlllie relay 105 operates but relay 106 being marginal does not attract its armature. The insertion Ot` the plug in the jack also completes a circuit for relay 200. This circuit may be tollowed from battery through the winding of the relay, lower lett contact ot sequence switch spring 201, upper lett contact et said spring, over the ring ot the trunk through the ring of jack 203 and plug 103, normal contact ot relay 109, normal contact or ringing key R K', winding ot coil 110, relay 108, normal ycontact ot relay 108, winding` otcoil 110,

upper normal contact ot key R K', tront conn tact ot relay 105, normal contact oi' relay 109, thence over the tip of the connection through the lett contacts of spring 202 to ground.

Relay 200 operates and closes a circuit as follows tor driving the sequence switch out of position 1 and into position 3: ground through the iront contact ot relay 200, right contact ot spring 206, through the winding ot the sequence switch magnet 205 to battery. When the sequence switch reaches position 23/4, a new circuit is closed for relay 200 traceable 'from battery through the winding of the relay, conductor 223, upper lett contact ot spring 207, back contact ot test relay 208, upper right contact ot spring 209 to ground. In position 3 oiA sequence switch 205 the sender selector switch, comprising the brushes shown at the bottom ot Fig. 2.` is operated to select an idle register sender 260. The brushes ot the sender selector switch are driven by a power n'iagnet 212 and the circuit tor this magnet may be traced from battery through its winding, upper right and lower lett' contacts of springl 213 to ground at the 'front'contactot relay 200. rlhe test for an idle sender is made by the test relay 208. rllhe circuit tor this purpose may be traced from ground through the lower right con tact ot spring 209, right high resistance winding ot relay 208, lower right Contact of spring 228 to the test brush 211. When an idle sonder is reached, battery of the proper potential being connected to the test terminal in the switch, the relay 208 operates and at its back contact opens the circuitr ot relay 200 which releases and opens the circuit of the power magnet 212 causingl the sender selector to come to rest. The relay 200 in releasing closes a circuit troni ground to its back contact, lowerleft contact ot spring 206 to the sequence switch magnet 205, driving the sequence switch out ot position 3 and into position a. In position 4 oit the sequence switch a circuit is completed from one pole ot battery through the usual impulse relay in the sender 260,` thence over conductor 222, brush 220, upper contacts oit spring 201, thence over the ring side ot thetrunk tothe jack and plug, normal contact ot relay 109, thence as previously traced through the winding ot relay 108 and returning over the tip oi the connection through the lower contacts of spring 202, brush 219, conductor 221 to the other pole oit battery in the sender. This circuit conditions the sender 'for the i'eceipt oit impulses and also operates the relay 108 to cause the illumination ot lamp 116. The operator seeing the lamp lightedat this time throws the dialing key DK. This key completes a circuit 'from ground to its lower contact, winding and normal contact of i'elay 109, winding ot relay 111 to battery. Relay 111 operates but relay 109 being inarginal remains inert. Relay 111 places ground potential on conductor 121 which may serve in the well known manner to associate the operators head set with the connection, or tor any other suitable purpose. l y

lhen the operator is ready to record the designation on the sender she manipulates the dial 112 in accordance with the digits ot the called number. Then the dial is moved away trom normal on the `first digit,` the springs 113 close and complete a circuit from battery through the resistance 115, springs 113, contact and winding' ot relay 109 to ground at the contact ot key DK. This shunts the relay 111 which releases and permits the relay 109 to operate and lock through its lett armature and contact. Relay 109 at its right armatures includes the tip and ring conductors in series with the contacts'lll of the dial 112. The dial on returning opens and closes the circuit leading to the impulse relay in the sender and the number is recorded in the well-known manner. After the dialing has been coinpleted the operator releases the key DK releasing relay 109. Relay109 disconnectsthe dial and includes the relay 108 across the tip and ring conductors ot the cord.

Duringl the registration the relay 21a is energized in circuit from battery through its winding, upper and lower lett contacts ot spring'- 215, brush 210, conductor 2liand thence to ground in the sender. TWhen the sender is prepared, the tundamental control circuit is completed -from battery to the winding` ot relay 200, conductor 223, lower lett contact ot spring 207, lower contacts ot spring 2211, conductor 235, brush 225 and thence through the stepping relay in the sender to ground. Relay 200 in operating closes the circuit for driving the sequence switch out ot' position l and into position 5. lWhen the sequence switch 205 reaches position A13/ the fundamental circuit is inodilied so as to lead from battery through the winding ot relay llO 200, lower contact oit spring 218, right con'-l tact or' relay 200 and thence over the lower contacts of spring 224 as above traced.

The brush selection is now made in the group selector by operating the brush tripping spindle 236. The circuitv for the trip Jindle magnet 227 may be traced trom battcrythrough the winding thereof, lower contacts ot' spring 213 to ground at the liront contact of relay 200. .its the trip spindle rotates the interrupter springs 237 open rand close to place a, shunt around the winding ot the stepping relay in the sender. This shunt may be traced from ground through the springs 237, lower right contactfot spring 207 to the winding ot' relay 200. Y This shunt circuit holds the relay 200 and releases the stepping relay in the sender. When the sender has beensatislied, the fundamental circuit is opened` and relay 200 releases. .Relay 200 on releasing opens the circuit of the magnet 22@1 stopping the tripping spindle in position to trip the proper set ot brushes and closes a circuit at its back contact for driving sequence switch 205 out of position 5. As thesequence switch reaches position 5% relay 200 is again oper ated in a circuit troni battery through its winding, Vconductor 223, upper lett contact ot' spring 207, back Contact ot relay 208, upper right contact ot spring 209 to ground. Relay 200 opens the circuit ot the sequence'switcli causing it to stop in position 6.

The brush carriage is now rotated by the power magnet 232 to select an idle trunk. The circuit for magnet 232 leads from battery through its winding, left handcontacts ot' spring 213 to ground at the 'front Contact of relay 200. During the moveinent'ot the brushes trom one trunk kto another' a test circuit is completed from ground through the lower right contact ot spring 209, right hand high resistance winding ot test relay 208, upper lett contact ofV spring 228, test brush 229 to the test terminals of the successive trunks. When an idle trunk is reached the proper potential is tound thereon to operate the test relay 208. 'Relay 208 at its back contact releases the relay 200 which opens tho Circuit ot magnet 232 and closes a circuit Jfor driving the sequence switch through position and into posit-ion 8. The test relay 208 in operating substitutes its lett hand low resistance winding'tor the right winding, thus rendering the selected trunk non-selectable to other switches. i

The apparatus is now in conditionr to oper ate the second group selector shown in Fig. 3 to further extend the connection. The fundamental circuit 'for controlling the group selector shown in Fig. 3 may be traced 'from the sender over the brush 225, conductor 235 lower right and upper left contacts of spring 224, brush 233, thence over the ring side of the trunk to the succeeding selector' andreturning over the tip side of the trunk through cuit is con'ipleted for operating the relay 406.

This circuit may be traced from battery through both windings o'lsaid relay, ett contacts oi spring 417, sleeve conductor 433 to the groundedpbrush 308. Relay 406locks through both its windings and lett -iront' contact and lthenormal contact of relay 403 to conductor-433. y y

Next theiinal selector "s positioned. under the control of the register sender and for this purpose the fundamental circuit is completed from battery through the winding ofrelay 400, lower and upper leift contacts of spring 416, conductor 430, thence over the ring side of the trunk lthrough the terminal and brush 307, contact oit spring 302, thence as pre viously tracedl to the sender 260 and returning over the tip side of the trunk through the upper contacts ot' spring 303, brush 306 to ground at the upper contact of spring 402. Relay 400 operates and locks through its winding and lett contact and the upper left i contact of spring 401 to the ring conductor ot' the trunk. VRelay 400 at its right-front contact completes a circuit leading throughthe lower 'right contact of spring 419 and the magnet 405 of the sequence switch for driving said sequence switch out of position 1 andinto position 2. In position 2 the brush tripping spindle magnet 422 is energized in a circuit from battery through its winding, lower lett and upper right contacts ot spring 418 to ground at the trout contact of relay 400. Magnet 422-rotates the brush tripping spindle to select the proper set of brushes and the interrupter springs 431 are opened and closed to place a short-ci'rcuiting path around the stepping relay in the sender. This path may be traced from ground through the` springs 431, upper right and lower'lett contacts ot spring 416 to the winding of relay 400. `When the lsender has been satisfied, the

fundamental circuit is opened and relay 400 'releases opening the circuit of the magnet .422, causing the tripping spindle to cease rotating. Relay 400k at its back'contact completes a circuit leading to the lower left contact of spring 419 for drivino' sequence switch 405 into position 3.

' VVhenthe sender is again ready, the fundamental circuit is reclosed and relay 400 operates to close a circuit for driving the sequence 405 out of position 3 and into position 5. YThe relay'400 locks as betere explained and with sequence switch 405 in position 5 the brush carriage power magnet 423 is energized. The circuit for magnet 423 leads from battery through its winding, right hand contacts of spring 418 to ground at the front contact et relay 400. Magnet 423 rotates the brush carriage. As the brushes 424, 425 and 426 pass each set olf terminals, the interruptor springs 432 opened and closed to shortcircuit the stepping relay in the sender. ,llhe path for short-circuiting this relay may be traced roin ground through the springs 432, upperright and lower left contacts ot spring 416 to the winding ot' relay 400. As soon as the hrushe, 424, and 426 reach the terminals oi the called line 427, the iund ainental circuit is opened in the sender causing the release ot 400. Relay 400 opens the circuit of the power magnet 423 and closes the circuit tor driving the sequence switch 405 out ot position 5.'

i As the sequence switch passes troni position to position (i the called line 427 is tested to determine its busy or idle condition. The test circuit leads 'from the brush 426, winding of test relay 420, contact of spring 421, resistance 428, lower right contact ot spring 413 to ground. li the line is idle relay 420 operate and loclrs through its lett iront contact `to ground at the right iront contact ot relayv 405. The sequence switch 405 continues to rotate until it reaches position 10.

When the sender has completed its control of the linal selector, it opens the circuit of relay 214 and this relay releases. Relay 200 now operates in a circuit through the upper lett contact ot spring 218 and the back contact ot' relay 214. Relay 200 completes a circuit for driving the sequence switch 205 out oi position 8 through position 9 and into po sition 10. As the sequence switch 205 moves into position 10 the slow release relay 204 is energized in a circuit from battery to its right winding, lower contact oi relay 240,`

lower lett winding ot repeating coil 242, lower right and upper lelt contacts of spring 201, thence over the ring side ot the connection to the operators cord circuit, thence through thev relay 108 as previously traced and returning over the tip side of the connection through the lower lett and upper right contacts oi' spring 202, upper lett winding o t' coil 242, upper contact oi relay 240, lett winding or relay 204 to ground. Relay 204 operates the slow relay 247 in a circuit i'roin battery through the winding ont the er relay, upper contacL oiE spring 24 Y .-48 to round at the contact oi' relay 204. Relay 47 closes an obvious circuit over relay 214. lilith relay 214 again energized a circuit is closed 'tor holding` the relay 200 traceable through the upper right Contact of spring 218 to ground at the iront contact of relay 214.

The circuits are now in condition to determine the character ofv ringing current that is necessary to operate the bell ot the called subscriber on the party line 427. lf the party line 42? has two subs'tations and it will also have two of terminals, rilhe upper set oft terminals appearing in the final selector switch shown relate to the sch The lower set or terminals rela f the substation 43o appear in l r group 'ci selector switches. Each ,c or is equipped with a ringing source 43?. By reversing the tip and ring conductors ot theparty line one substation is signal il when the line is seized by one group oit connectors whereas the other substation is 'nalcd when the line is seized by the other roup et connectors.

inasmuch as ringing current is supplied troni the lirst group selector switchL shown in 2 when the toll operator recalls, it is necessary to provide some identitying ineans in the "inal switch. This nieans consists oi" a resist- 19 in one group of linal seince element 4er. Y iectors the resistance element is provided in series with the resistance 439. in the other group of final selectors che resistance 438 is oi'uitted and the resistance 49S) is connected directly to the upper right Contact of spring 4t2. ln the presentinstance assuine that the substantion 434 is called and that the iinal selectors having access to this substation are equipped with the resistance 438. lfilhen the sequence switch 405 reaches position 9%, a circuit is completed from battery through the resistances 48S and 438, right contacts oit spring 412, conductor 430," thence over the ring` side oil the connection to the brush 233, lower back contact oi' relay 240, right contacts of spring 245, right windings oi relays 250 and 251 to ground. 'lhesc two relays serve to identity the substation called and to prepare ior the application oi' either the ringing source 252 or when the toll operator recalls the called subscriber. Since the resistance 438 is included in the circuit treed the marginal relay 250 does not operate. Relay 251, however, operates and locks through left winding and contact, lower rigl'it contact oit spring 248 to ground the contact ot relay 204.

lielay 251 in operating closes a circuit troni ground through its outer left iront contact, upper lett contact ot spring 205, magnet- 205 to battery. Vlfhe sequence switch thereupon nieves out ot position l0 and ito position 11 where it awaits the toll operator. As the sequence switch 205 leaves position l0 it opens the circuit of relay 200 vr l When spring 248. Wit-h the sequence switch 205 inv position 11 as explained and the operator applying ringingcurrent to operate the relay 241, a circuit is closed for the relay 200. This circuit may be traced from battery through the windingy of said relay, lower left and upper right contacts of spring 249, contact of relay 241 to ground at the back contact of relay 243. Relay 200 at its front contact closes a circuit for driving the sequence switch 205 out of position 11and into position 12. As sequence switch 205 leaves position 11 relay 200 releases. When the operator ceases to manipulate the ringing key R K relay 240 releases and relay 204 is again operated as explained.

The linal selector is now ready to advance into the ringing position. Whenthe sequence switch 205 of the group selector reaches position 12 a circuit is closed from battery through the winding of relay-400, lowerleft contact ofy spring 416, lower left contact ot spring 415, resistance 440, thence over the tip sideof the connection through the brush 234, upper back contact of relay 246,.lower right and upper left contact ot spring 244, upper right winding of repeating coil 242, upper winding of relay V243 to. ground. Relay 400 operates but due tothe resistance 440 f relay 243 remains inert.- ;v Relay 400 closes an line and returning by way kof brush 424, upper spring 404 right and lower left contacts of l through the-windingot the ringing relay 403 to battery, Relay 403 doesnot operate until the subscriber removes hisreceiver. As soon after the sequence switch reaches position 12 as the'interrupter 441 closes its lower contact, a circuit is completed through the 'lower right contact Vof spring415 and the winding of relay 400. Relay400 operates, closing the circuit for advancing the sequencek switch out of position 12 and intoposition 13. The closure of the yinterrupter-44l is-otsuch brief duration that relay 400 releases before se# quence switch 405 can move out of position 13. As soon after the sequence switch reaches position 13 as the interrupter 441 closes its upper contact a similar circuit is completed for operating relay 400 to advance the sequence switch out of position 1?` into position 14. In position 14 ringing current from the machine ringing source 437 is applied to the called subscriber-s line. When the'called subscriber answers therelay 403 operates and opens the holding circuit of relay 406. Relay 406 releases and at its back contact completes a circuit l'or moving' the sequence switch 405 out of position 14. When sequence switch 405 reaches position 145/8 relay 406 operates in a circuit from battery through its right winding, right contacts of spring 417 to ground. Relay 406 opens the. driving circuit of sequenceswitch 405 causing the sameV to stop in position 15. Relay 406 locks in a circuit from battery through both its windings, `left contacts of spring 417 tothe sleeve conductor 433. f The final selector switch is now; in itst-alking position. i

back contact of relay 246 thence over the ring side of' the connection tothe linal selector through the upper right contact of spring 401,

brush 425, over the subscriber-s line, brush 424, upper contacts of s pring404, thence over the tip side of the connection throughthe upperback contact oi' relay 246, lower right and upper left contacts of spring 244, upper right winding of the coil 242, upper winding of revlay 243 to ground. Relay `243 operates, and closes a circuit from ground through its frontV contact, lower-contacts of springA 249, winding of relay 200 to battery. Relay 200 operates, closing the circuit for driving the sequence switch 205 out of position 12 and into position 13. As the sequence switch leaves position 12 it opens the circuit of relay 200. The group selector shown in Fig. 2 is now in its Atalking position.

With t-he subscribers receiver connected across the line at the called'substation a ciriio f 1115 In position 13 of sequence switch 205, a cirf cuit is closed from battery, through the lower Y winding ofrelay 240,'rightcontacts of spring V249 to ground at the front contact of relay 243." Relay 240 operates and opens the circuit of relays 204 and 108. Relay 108 extinguishes the-lamp 116 as a signal to the operator that the called subscriber has answered.

' At the end of conversationY the subscribers replace their receivers. The called subscriber.v

operator. Inthewell known manner the replacement of the calling subscribers receiver gives a signal to the toll operator. The operator takes down the connection by disconnecting her cord circuit. rilhis causes the release or relay 204 which in turn releases rclays 247 and 214, Relay 200 operates in a circuit over the lett contact 4ot spring 218 and the' back contact ot relay 214. Relay 200 com letes a circuit for drivin@ the se uence switch 205 out of position 13 and into position 17. In this position the brush carriage is restored to normal. The circuit for the magnet 232 leads over the lett contacts ot spring 213 and the :front contact ot relay 200. The relay 208 is in a deenergized condition at this time since its circuit was opened. when the sequence switch moved out ot position .3. Relay 200'is energized at this time in a ci reurt from battery, through 'its winding, upper leit contact of spring 207, back contact ot relay 208, upper right Contact ot spring 209 to ground. `rWhen the brush carriage rea-ches its normal position, a circuit is closed 'trom hattery, through' the normal contact and brush 257 uo 3er rioht Contact ot serine' right 7 D l. C) 9 u:

vwinding ot relay 208, lower right contact of spring'209 to ground. Relay 208 operates and releases relay 200 which opens the circuit for the power magnet 232.

It will be noted that the tripping spindie 236 is restored as soon as the sequence switch 205 reaches position 12. The circuit for this purpose may e traced trom battery, through the winding of magnet 227, right contacts ot spring 215, to ground throughthe springs 237. y

The opening ot the sleeve lead causes the release ot the second group selector shown in Fig. 3 in the usual manner.

The opening 'ot the sleeve leadv also re leases the relay 406 in the tinal selector Re lay 406 completes a circuit over the spring 419 Jor driving the sequence switch 405 out oit position 15. It the called subscriber has replaced hisreceiver, relay 406 remains deenergized and sequence switch 405 is driven into position 17. In this position the tripping spindle is restored to normal by means oi' af circuit trom battery, tl'irough the winding of magnet 422, lower lett and upper right contacts ot spring 418 to ground at the trent contacts ot relay 400. Relay 400 is energized at this timein a circuit -from battery through its winding, lower contacts o'l spring 413 to' groundthrough the springs 431. When the tripping spindle is restored spring 431 opens and releases relay 400 in turn opening the circuit of the magnet 422. Relay 400 in releasing closes a circuit Jfor driving the quence switch out of position 17 and intoV position 18. The brush carriage is restored by means ot' a circuit from battery, through the winding of magnet 423, lower right andV upper lett contacts ot spring 418 to Iground at the back contact of relay 400. -When the It will next be assumed that the called subscribers line is busy at the time it is tested. The relay 420 therefore tails to operate and when the sequence switch reaches position 8% the relay 400 energizes. rilhe circuit may be traced 'from battery, through the winding ot said relay, spring 414, back con-V tact oli relay 420, to ground at the contact oi relay 406. Relay 400 opens the circuit of the sequence switch causing it' to stop in position 9. In this position a busy signal is sent back to the toll operator. For tl is purpose the relay 408 is operated in a circuit from bat tery, through its right Winding, right contacts of spring 40S-to ground at Vthe frontcontact ot relay 400. Relay 408 'completes a circuit from battery,through the interrupter 442, right contact of relay 408, right VContact ot spring 402, thence over the tip side of the connection, right contacts of spring 244, upper winding ot relayl 240 to ground, through the lett bach contact of relay 251. Relay 240, under the control of interrupter 442, operates and releases intermittently, opening the circuit of relay 108 in the operators cord circuit. This causes the lamp 116 to iiash indicating that the line is busy. The operator causes the release ot the apparatus in the well known manner.

It will next be assumed that after the con'- versation has been completed the called sub-- scriber is the first-to hang up his receiver and that the tollv operator wishes to recall him without releasing the connection; .4t this time it will be remembered, the sequenceswitch 205 is in position 13 and the sequence switch 405 is in position 15. To vr call, the toll operator manipulates her ringingv hey R K to operate the relay 241 as previously explained. Relay 241 operates relay 240 and a circuit is now closed :tor relay24 IThis circuit leads from battery, through the" wind ing of relay 246, inner right contact of relay 251, lower right contact o1" springr254, inner upper contact of relay 240, bach contact of relay 243 to ground. Relay 246 connects ythe ringing source 252 with the tip andfring con-- ductors ot the connection leading to the calli-ad? subscribers line. The ringing circuitvis traced from the source 252, right baclrconi tact of relay 250, outer right fron-t contact of relay 251, lower front contact et relay'246, thence over the ring side of the connection, through the subscribers line and returning over the tip side to ground at the upper iront contact of relay 246. This ringing source is the proper hind to operate the subscribers bell zit-substation .434.y Had the Vother sub-l as disclosed inthe patent to McBerty and Polinlrowslty hereinbefore cited.

l/Vhile the invention is shown in conne@` tion with switches of the rotary power driven type, it is to be understood that it is not limited to a system employing such switches,

-but may be applied as wellrto other types of systems. l K

IWhat is claimed is: l. In a telephone system, telephone lines, a series of selective switches, means for operating said switches to extend a connection to a called telephone line, a plurality of sources of ringing current, each associated with a different switch in said series, and means for applying ringing current to the called line from all ofsaid sources. n

2. In a telephone system, telephone lines, a series of selective switches, means for 'operating said switches to extend a connect-ion to a called telephone line, a yplurality of sources of ringing' current, each associated with a different switch in said series,'auto matically operated means for applying ringing current to the called line from one of said sources, and manually controlled means for applying ringing currentto the sam-e called line from another of saidsources. l

3. In a telephone system, telephone lines',

a series of selective switches, means for operating said switches to extend a connection to a called telephone line, a plurality of sources of ringing current, each associated with a dierent switch in said series, an operators position, automatic means forconnecting one of said sources to a called line to call the subscriber, and means controlled by the operator to connect another of said sources to the line to recall the subscriber.

l. In a telephone system, subscribers lines, a group selector and a iinal selector switch, means for operating'said selectors in succession to extend a connection to a called line, a separate source of ringing current associated with each selector, and means `for applying current to the same called line from both of said sources.

5. In a telephone system, telephone lines, a series of selective switches, means for operating said switches to extend a connection to a called telephone line, a source of ringing current associated with one of said selective switches, sources of ringing current of different characterA associated `witha second switch in said series, andvmeans for apply-ing toa called-line ringingcurrent from any of said sources.

6.v In a telephone system, party lines, a series of selective switches, means for operating 'said switches to extend av connection to a called line,-a'source of ringing current associated with the final one of said switches for signalingthe*subscribers on a party line, sources of ringing current associated with a' preceding selector in t-he series, means effective when a party line is called for connecting thereto the source associated with the linal selector, and means effective whilel the same talking connection is maintained to the called line for connecting one of the sources associated with the preceding selector to said called line. Y

7. In combination, subscribers lines, a series of selectors for extending a connection 'to a called line, a plurality of ringing sources associated with one of said selectors, a variably applicable source associated with a subsequent selector'in the series, means for con necting to a called line the source at said subsequent selector, and selective means controlledA by said subsequent selector for connecting to the called line'the desired one of said sources at said first selector.

8. In combination, subscribers lines, a series of selectors for extending a connection to a called line, a plurality of ringing sources associated with one of said selectors, a variably applicable source associated. with a sub sequent selector in the series, means for connecting to a called line the source atsaid subsequent selector, identifying means in said first selector, means for setting said identifying means according to the manner current is applied'at the subsequent selector, and means controlled` by said identifying means for selectively connecting to the called line one ofthe sources at said first selector.

9. In combinatiomvparty lines, a series of selector switches for extendingra connection to a called party line, ringing sources of different character associatedfwith one of said switches, a ringing source associated with a subsequent switch in the series, means de-V pendent on the party called for Variably connecting to 'the line the source of current at said subsequent switch, means dependent on the party called and controlled from said subsequent switch for establishing in said first switch a record identifying such party, and means controlled by said identifying record for selectively connecting to the called line one of the sources at said lirst'selector.

10. In combination, party lines, a plurality of groups of Vfinal selector switches, each group having access to said lines for the purpose of calling a different party thereon, a group selector switch for extending a connection to any one of said final selector switches, a source of ringing current associated With each of said final selector switches, sources of ringing` current associated with said group selector, nieans dependenton the party called for variably connecting to the called line the source ofvringing current at the final selector, and identifying' means in said group selector operable in accordance with the group of final switches to Which the connection is extended for'selectively connecting to the called line one of the sources o'i ringing current at said group selector.

1l. In a telephone system, subscribers lines, a series of selector switches for extend ing both local and toll connections to a called line, a. source of ringing current in the final selector YFor signaling the called line on both local and toll calls, a source of ringing` cui'- rent associated with a preceding selector in said series, ano'nieans for rendering` said last source ellective to signal the called line When a toll call is extended thereto, g

In Witness'whereof, l'hereu to subscribe my name this 28th day of April, A. 1927.

e-eoeen rrioMPsoN. 

